Perfluoroalkyl-substituted polymers possess free surface energies even lower than that of polytetrafluoroethylene. They have therefore long been used to impart oil- and water repellency to a wide variety of substrates, especially textiles. Additionally, phosphate esters of perfluoroalkyl-substituted alcohols are being used as oil- and water-repellent paper sizing, for instance in paper plates and in food packaging products. For such applications, it is especially important that the paper sizing compound contain at least 2 R.sub.F -groups, where R.sub.F is a perfluoroalkyl group. When mono-R.sub.F -alcohols are used to esterify phosphoric acid, only the diesters are active oil- and water-repellents; the monoester is too water soluble and, even if retained on the cellulose fiber, reduces water repellency, and the triester is not substantive. Making phosphate diesters in high yield is, however, very difficult in practice; substantial amounts of mono- and triesters are always produced as by-products.
Typical fluorinated mono-alcohols are perfluoroalkyl-alkanols, such as 3-perfluoroalkyl-propene-2-ol. See J. Fluorine Chem., 20(3), 313-27 (1982), DE 23 33 935 (1974), DE 22 55 672 (1973) and FR 1 473 451 (1967). Such monofunctional alcohols, while suitable for the preparation of acrylic and methacrylic oil- and water-repellent R.sub.F -polymers, are less suitable for the preparation of oil- and water-repellent phosphate esters for reasons given above. Likewise, it is also impossible to prepare oil- and water-repellent sulfuric acid half esters from mono-R.sub.F -alcohols since such esters are very water soluble anionic surfactants. For the preparation of oil- and water-repellent polyurethanes it is especially important that the diol contain more than one R.sub.F group.
Using di-R.sub.F -alcohols makes it possible to prepare oil- and water-repellent phosphate or sulfate monoester paper sizes, since even a monoester contains two R.sub.F -groups. Certain di-R.sub.F -diols are described in U.S. Pat. Nos. 3,935,277 and 4,946,992. Said patents describe the synthesis of di-R.sub.F -alcohols and diols by reaction of R.sub.F -ethylenethiol with halogenated alcohols and diols.
Polyurethanes of di-R.sub.F -diols are described in U.S. Pat. Nos. 3,968,066, 4,046,944, 4,054,592 and 4,098,742. Phosphate esters are described in U.S. Pat. Nos. 5,091,550 and 5,132,445. Although the di-R.sub.F -phosphates show excellent performance, their synthesis involves many steps and costly intermediates. Similar compounds produced by a more straightforward synthesis route and preferably lacking the thermally unstable thioether linkage would be highly desirable.
It has now been discovered that di-, tri- and poly-perfluoroalkyl-substituted alcohols which fulfill these requirements can be prepared in high yields from perfluoroalkyliodides and di-, tri- or polyallyl alcohols or acids. These compounds have not previously been described. They are useful by themselves or as intermediates for making end products which impart outstanding oil and water repellency to textiles, paper, leather, wood and other substrates.
Sugar derived perfluoroalkyl substituted polyols have been synthesized earlier, namely from xylitol, galactose, and glucose; see Bull. Soc. Chim. Fr., 872-8 (1989), J. Med. Chem., 33(4), 1262(1990) and U.S. Pat. No. 4,985,550. Such polyols, with a hydroxyl functionality of three or more, are not suitable for preparing linear polymer compositions since crosslinking is likely to occur.